Xeropilidium dennisii

Xeropilidium dennisii Baral, Pärtel & G. Marson, IF:815744
= Encoelia fuckelii Dennis, Kew Bull. 25(2): 348 (Dennis 1971), nom. illegit. ICN Art. 53.1 [non Encoelia fuckelii (Sacc.) Boud., Hist. Class. Discom. Eur. (Paris): 161 (Saccardo and Traverso 1907), (?) = Velutarina rufoolivacea, see Baral and Perić (2014)].
Holotype TU 104501, ex-type culture TFC 201986
Apothecia gregarious, in fascicles of 2–6, hydrated (0.5–)1–2(−2.7) mm in diam., cupulate to saucer-shaped or finally flat, distinctly gelatinous, resembling a Mollisia, receptacle 0.3–0.45mm thick; disc rehydrated milky whitish-cream to bright grey to brownish grey, shining, seemingly waxy, semitranslucent; outside bright grey to dark olive- to blackish-brown, covered with white pruina, margin light reddish- to dark olivaceous-brown; subsessile with a hidden stalk ~0.3–0.6 × 0.25–0.6 mm, stalks always separate, erumpent from beneath the periderm, inserted on bast; receptacle compressed when dry, hysteriform to triangular. Ectal excipulum 150 μm thick near the base, 30–50 μm at flanks, 20 μm near margin, of vertically oriented t. angularis(−prismatica), cells *7–12 × 4–8 μm (†3–11 × 1.5–3 μm), wall strongly swollen in dead state (†0.8–1.5 μm), with bright reddish-ochre to dark brown exudate towards the outer surface, continuously paler yellowish-amber inside, exudate not dissolved or changing
colour in KOH, ± indistinctly separated from medullary excipulum by a t. porrecta. Medullary excipulum hyaline, upper part 60–80 μm thick, of slightly gelatinized t. porrecta oriented perpendicular to disc surface (paraphysis-like), hyphae *1.5–3 μm wide; lower part 70–90 μm thick, of gelatinized t. intricata forming a thin t. porrecta near ectal excipulum, cells *2–5 μm wide (†1.5–3.5 μm), with gelatinous coat being strongly swollen in dead state. Asci narrowly clavate, *42–85(−105) × 4.5–5.8 μm {5}, †(33–)38– 60(−70) × 3–4.5 μm {3}, 8-spored, spores ~3–4-seriate, pars sporifera *12–22 μm long; apex rounded to medium truncate, IKI- {6}, MLZ-, with apical thickening †1.5–2.2(−3.5) of juvenile asci, 1–1.3 μm of mature asci {6} (*0.3–0.4 μm); gradually tapering into a short to very long stalk, arising from small croziers {5}. Ascospores narrowly cylindrical, sometimes ellipsoid or ± clavate, straight, rarely slightly curved, hyaline, *4.5–8(−10) × (1.2–)1.4–1.8(−2) μm {5}, †4.2–8 × 1–1.5 μm {2}, aseptate, containing 0–4 min LBs (0.1–0.2 μm); exceptionally seen to form conidia at their ends. Paraphyses filiform, equally septate, terminal cell ~12–22 μm long, simple or branched in the upper ¼, ± flexuous to bent or even hooked, surrounded with small crystals, exceeding the dead asci (but living asci projecting 0–10 μm), *1–1.5(−2.2) μm wide {3} (†0.7–1 μm), containing a few minute LBs, without VBs. Abundant hyaline to pale yellowish, cloddy-amorphous (resinous) granules loosely interspersed between paraphyses {2}, abundant also in medullary
excipulum, staining turquoise(−blue) in CRB. Hyaline mass of crystals covering flanks and margin {9}, each ca. 2–5 μm in diam., rhomboid, partly forming druses, more sparse on hymenium and in medullary excipulum.
Synanamorphs: 1) Sporodochial, in culture Colonies 5 cm in diam. (while 3 months old), slow growing on MEA, radial growth 9 mm /week. Aerial mycelium lacking, except for the margin. Marginal zone fimbriate, slimy, hyphae on surface branching; subsequent zone ca. 1 cm, formed of sparse hyphae covered with crystals; the central zone of submerged hyphae. Sporodochia densely formed in central part of the colony and sparsely over the rest of the colony; sessile or with a submerged short stipe; 0.4–0.9 mm wide and up to 1.2 mm high, pale ochraceous; formed singly or aggregated; initially cupulate, sometimes with horizontal outgrowths or irregularly cushion-shaped, later covered by a clavate-spherical, slimy and shiny, cream-coloured conidial mass. Conidiomatal wall paler than conidial mass, appearing rough due to external crystals, 5–10 μm in diam.; outermost cells hyaline, thin-walled, 6–10 μm in diam., septate, forming t. angularis-globulosa; inner part t. intricata, of hyaline, septate cells, 2.5–4.6 μm in diam. Conidiophores hyaline, septate, di- to trichotomously branched, forming whorls of conidiogenous cells in the basal part, 3–6 branches formed from one point, one branch often up to two times longer than others; 0.8–1.5 μm wide near the base, tapering gradually toward the apex, smooth-walled, individual cells 6–8 μm long. Conidiogenous cells terminal, subcylindricsublageniform, hyaline, 6–12 × 1.3–1.7 μm, phialidic, with an inconspicuous collarette at the conidiogenous locus at the apex. Conidia cylindric-ellipsoidal, straight, hyaline, thinwalled, aseptate, smooth, with two small guttules, *2.7–3.5 × 0.8–1.3 μm. Isolate examined: TFC 201986, inoculated from ascospores from the holotype specimen TU 104501 by G. Marson. 2) Pycnidial, on natural substrate Pycnidia growing next to apothecia or found on separate branches, singly or in fascicles of 2–10 by arising from a common stromatic base, globose to broadly ellipsoid or subangular, 0.25–0.6 × 0.25–0.35 mm, with minute papilla from which a slimy conidial drop emerges; greyish ochrebrown when moist, upper half whitish-grey and pruinose when dry due to a dense cover of crystals; stipitate, erumpent from beneath the host’s periderm, on bast; stalk blackish redbrown, up to 0.35 mm high, laterally compressed. Conidiophores di- to trichotomously branched or verticillate (up to 6). Conidiogenous cells *8–14 × (1.2–)1.4–1.7 μm {2}, subcylindrical-sublageniform, tapering gradually towards the apex, phialidic, without or with an inconpicuous collarette. Conidia cylindrical to sometimes ellipsoidal, straight, mostly with 1–2 min guttules, *(2.5–)3–3.7(−4) × 1–1.4 μm {4}. Hyaline setae emerging abundantly from basal branches of the conidiophores {3}, up to 100 μm long, 1.7 μm wide at the base, gradually tapering towards the pointed apex, thin-walled, hyaline, with oil drops near the septa.
Habitat: on thin, corticated, xeric, still attached branches of Cornus sanguinea {1}, Crataegus spp.{4}, Prunus spinosa {4}, Rosa spp. {2} and Salix spp. {2}, 1–3 m above ground, or on cut branches lying in piles, host bark often detaching, erumpent through periderm of bark {14}. Phenology: from autumn to spring (Oct–Jun).
Distribution: rare in Europe (Spain, Luxembourg, Germany, United Kingdom, Sweden).
Comments: Based on the illegitimacy of E. fuckelii Dennis,m we recommend changing the specific epithet and describe Dennis’ fungus as a new species in a new genus. We designate as the holotype a recently collected specimen for which, in addition to the sexual morph, supporting asexual morph and DNA-associated data are available. In the multigene phylogeny X. dennisii forms a group with species of the originally anamorph-typified genera Pilidium Kunze and Chaetomella Fuckel, members of Chaetomellaceae (Baral 2015). The affinities of this recently described family in Leotiomycetes, which is distinct from any other family or order, are not yet resolved (Rossman et al. 2004; Wang et al. 2006a; Johnston et al. 2014a). The phylogeny presented herein as well as analyses of the morphology show that X. dennisii was misplaced in the genus Encoelia by Dennis (1971) , but support its inclusion in the Chaetomellaceae. Until now this family, which includes 4 genera and c. 80 species (Baral 2016), comprised only two species with a known teleomorph. In both cases an earlier name based on the type containing only the anamorph was recently protected against a later name described for the teleomorph, viz. Pilidium lythri (Desm.) Rossman over Discohainesia oenothera (Cooke & Ellis) Nannf. and Chaetomella oblonga Fuckel over Zoellneria rosarum Velen. (Johnston et al. 2014b). The teleomorph characters shared by these two species and X. dennisii are the inamyloid asci and the extracellular resinous drops among the apically branched paraphyses. P. lythri, as studied by Shear and Dodge (1921), resembles X. dennisii also in forming subsessile apothecia with a pale disc and reddish-brown ectal excipulum comprised of isodiametric cells becoming more elongated towards the margin. Both species are characterised by a paraphysoid upper medullary excipulum, narrow, apically branched paraphyses forming a waxy epihymenial cover, and asci with a tapered base. The sexual state of Chaetomella oblonga differs from the other two by having short, narrow apothecial stipes which are, like its pycnidia, densely covered by brown setae. These three genera of Chaetomellaceae share similar synanamorphs. The pycnidia and sporodochia of Xeropilidium resemble those in the genus Pilidium as described by Palm (1991) and Rossman et al. (2004) as well as in Chaetomella (Rossman et al. 2004). However, the morphs of both Pilidium and Chaetomella lack the crystals characteristic of X. dennisii. Species of Chaetomella differ by forming conspicuous brown setae on both the ana- and teleomorph (Rossman et al. 2004; Johnston et al. 2014a). Pilidium and Chaetomella are either plurivorous or host-specific, growing
as weak parasites on leaves or stems, and on fruits of various dicots. Xeropilidium dennisii is the only member of Chaetomellaceae that grows on bark of trees or shrubs. It also is drought-tolerant, as paraphyses and anamorph remain viable after a 1.5 months stay in the fungarium. The phylogeny drawn
from multigene data (Fig. 1) and ITS rDNA characters (Fig. S6) revealed the distinctness of Xeropilidium dennisii within the family. The three ITS sequences derived from specimens were identical not only to each other but also to one INSD sequence from the European elm bark beetle from Scandinavia.
Type specimens examined: LUXEMBOURG, 7 km SE of Luxembourg, 2 km ESE of Alzingen, Héid, 49.5635°N 6.195°E, alt. 300 m, branches of Crataegus sp., on bark, 21 Feb. 2013, G. Marson (TU 104501, holotype, ex-type culture TFC 201986, INSD accession number LT158441).
Specimens examined: UNITED KINGDOM, West Sussex, 2.5 km N of Ardingly, Wakehurst Place, 51.0695°N 0.0845°W, alt. 135 m, on bark of Prunus spinosa, 7 Apr 1968, R.W.G. Dennis (K(M) 31,026 as holotype of E. fuckelii nom. illegit.), Cambridgeshire, 9 km NNW of Huntington, Monks Wood National Nature reserve, 52.4°N 0.24°W, alt. ~40 m, on bark of an unidentified tree, 15 Oct 1960, R.W.G. Dennis&E.
Milne-Redhead, det. R.W.G. Dennis (K(M) 42,869). LUXEMBOURG, Gutland, Luxembourg Plateau, 5.5 km NNW of Luxembourg, 1.5 km E of Bridel, Plakigebierg, 49.66°N 6.11°E, alt. 280 m, branch of Crataegus monogyna, on bark, 5 Jan. 1992, G. Marson (H.B. 4582); 6.5 km E of Luxembourg, 2 km S of Sandweiler, Weierboesch (W of Kallecksuewen), 49.60° N 6.215° E, alt. 330 m, branch of Prunus spinosa, on bark, 19 Jan. 1990, G. Marson (H.B. 3964); 4 km S of Luxembourg, 1 km NE of Kockelscheier, Laangeweier, 49.565°N 6.125°E, alt. 305 m, P. spinosa, 15 Mar 1988, G. Marson (G.M. 3627); 5 km S of Luxembourg, 1.5 km W of Hesperange, forest between Biersak and Géisselbierg, 49.57°N 6.13°E, alt. 290 m, branches of Salix, on bark, 7 May 2004, G. Marson (ø); Terres rouges, 1 km E of Bettembourg, Bierg, 49.52°N 6.12°E, alt. 285 m, branches of Crataegus sp., on bark, 14 Nov 1991, G. Marson (H.B. 4557); 1.7 km NNW of Esch-sur-Alzette, 1.3 km SE of Ehlerange, Laankelzer Boesch, 49.515°N 5.98°E, alt. 300 m, branches of Crataegus sp., on bark, 12 Jan. 1990, G. Marson (G.M. 4018, H.B. 3959); ibid., branch of Rosa canina, on bark, 2 Feb. 1989, G. Marson (G.M. 3813, H.B. 3673). 2 km NNE of Dudelange, 1.5 km S of Bettembourg, railway, 49.505°N 6.097°E, alt. 275 m, branch of Salix caprea, on bark, 20 Jun 1998, G. Marson (H.B. 6173b); Velée de Moselle, 6 km NNE of Grevenmacher, 2 km NW of Wasserbillig, WNW of Langsur, 49.726°N 6.48°E, alt. 254 m, branch of Cornus sanguinea, 14 Dec 2014, G. Marson (ø). GERMANY, Nordrhein-Westfalen, 7 km NE of Gelsenkirchen, 3.7 km SSE of Herten, Hoppenbruchhalde, 51.562°N 7.153°E, alt. 60 m, branch of Rosa, on bark, 23 Feb. 2006, F. Kasparek (M-0281058/ H.B. 8071, TU 104524, KL159). SPAIN, Asturias, 18 km SSE of Pola de Lena, 2 km SSW of Pajares, Hayedo de Valgrande, 43.00°N 5.78°W, alt. 1035 m, branches of Prunus spinosa, on bark, 6 Jun 2009, E. Rubio (E.R.D. 4818, d.v.).